U.S. Pat. No. 4,114,785 granted Dec. 11, 1978 discloses a pneumatic outlet including a control valve having a moment portion and a body portion. In closed position the control valve closes an opening between the lower inner edges of sloping outlet side walls. The moment portion and the body portion each have an edge portion which in closed position engages an adjacent seat portion located on a sloping outlet side wall.
However, with hard plastic pellets such as lucite, high density face cut polypropylene and face cut polystyrene, a problem has developed in operation of the outlet. When the valve is rotated from the open position to the closed position, hard pellets may become trapped between the moment portion edge and its valve seat. A similar problem, although less frequently, occurs when the body portion edge engages its adjacent seat. When pellets become trapped between the moment portion edge and and its seat, and/or the body portion edge with its seat, it sometimes becomes very difficult or impossible to completely close the control valve if required such as after sampling, suspended unloading or switching from one side to another.